09intanceof 和类型转换

public class Application {
    public static void main(String[] args) {
       //Object>String
        //Object>Person>Teacher
        //Object>Person>Student
        Object object =new Student();
        //System.out.println(x instanceof y);//编译是否通过，就看x和y是否存在继承关系！
        System.out.println(object instanceof Student);
        System.out.println(object instanceof Person);
        System.out.println(object instanceof Object);
        System.out.println(object instanceof Teacher);
        System.out.println(object instanceof String);
        System.out.println("========================");
        Person person =new Student();
        System.out.println(person instanceof Student);
        System.out.println(person instanceof Person);
        System.out.println(person instanceof Object);
        System.out.println(person instanceof Teacher);
        //System.out.println(person instanceof String);编译报错！
        System.out.println("========================");
        Student student =new Student();
        System.out.println(student instanceof Student);
        System.out.println(student instanceof Person);
        System.out.println(student instanceof Object);
        //System.out.println(student instanceof Teacher);编译报错！
        //System.out.println(person instanceof String);编译报错！
    }
}
运行结果：
true
true
true
false
false
========================
true
true
true
false
========================
true
true
true

类型转换：

1.父类引用指向子类的对象

2.把子类转换为父类，向上转型

3.把父类转换成子类，向下转型：强制转换

4.方便方法的调用，减少重复的代码！简介

public class Person {
    public void run(){

    }
}

public class Student extends Person{
    public void go(){
        System.out.println("go");

    }
}

public class Application {
    public static void main(String[] args) {
        //类型之间的转换  基础类型转换：高转低（强转），低转高直接转换
       //类型之间的转换:父  子
        //子类型转换为父类，可能丢失自己本来的一些方法
        //高                 低
        Person obj=new Student();
        //student将这个对象转换为Student类型，我们就可以使用Student类型的方法了
        Student student =(Student)obj;
        student.go();

        Student student1 =new Student();
        student1.go();
        Person person=student1;
         }
}